[clang] [NFC][clang] Avoid inheriting [[noreturn]] in explicit function template specializations (PR #150003)

[Yanzuo Liu via cfe-commits]

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zwuis wrote:

Can you add this test case?
```cpp
template<typename T> 
 struct S { 
   void f(); 
 }; 
  
 template<typename T> 
 void S<T>::f() {}  
 template<> 
 void S<int>::f() { throw 0; }
```

https://github.com/llvm/llvm-project/pull/150003